1. Field of the Invention
The present invention concerns controlling and guiding the displacement of a mobile member parallel to an axis and minimizing any unwanted tilting of the mobile member relative to the axis.
2. Description of the Prior Art
The invention is particularly, but not exclusively, directed to guiding and controlling the movement of a lens within a focussing mechanism of optical instruments or telescopes; in such optical instruments it is necessary to move one or more lenses to achieve optimum focussing and this displacement must be exactly aligned with the direction of the optical axis on which the lens is disposed.
The quality of the image formed by the optical instrument in question depends on the quality of the lenses and also on how accurately they are positioned on the optical path. It is therefore essential to guide and control the displacement of the lens in such a way as to minimize positioning defects.
There are two types of lens positioning defects, which may be encountered in combination:
firstly there is eccentricity, that is to say a parallax defect between the lens axis and the axis of the optical path of the radiation passing through the lens; PA1 then there is tilting, that is to say an angular offset between the axis of the lens and the optical axis. PA1 the transverse extension of the mobile member is to a same side of the flexible plates in the direction parallel to the axis being that the transverse extension is longitudinally outside the pair of flexible plates and not between these plates; PA1 the actuator comprises a plunger in simple bearing engagement with the extension, parallel to the axis, and the flexible plates are resilient; PA1 the transverse extension of the mobile member is located, in the direction parallel to the axis, between the actuator and the pair of flexible plates; PA1 the translation axis is horizontal and the mobile member is suspended from the fixed member by the plates which are symmetrical relative to a vertical plane perpendicular to the horizontal translation axis. PA1 the mobile optical member is a ring in which a lens is mounted; PA1 the translation axis is horizontal and the ring is disposed in a vertical plane; PA1 the ring is linked to the frame by the single pair of flexible plates symmetrical relative to a vertical plane perpendicular to the translation axis.
The latter type of defect is usually more prejudicial to image quality.
The invention is mainly directed to minimizing or even eliminating this latter type of defect while minimizing eccentricity.
The invention is directed to obtaining the aforementioned result in a simple, reliable, inexpensive and compact manner by using mechanical guidance free of play and friction and requiring force to be applied at one point only to carry out the displacement.